In a conventional electrographic image forming apparatus, such as printers, photocopy machines, facsimile machines, multifunctional peripherals and the like (e.g., printer here as an example), a photosensitive drum, a charge device, a light emitting diode (LED) head, a development unit, a transfer roller, a cleaning device, a fuser and the like are arranged. An electrostatic latent image is formed by exposing, using the LED head, a surface of the photosensitive drum that has been uniformly charged by the charge device. The electrostatic latent image is developed by the development unit to form a toner image on the surface of the photosensitive drum. Then, the toner image is transferred to a sheet by the transfer roller and fixed onto the sheet at the fuser. In addition, the toner remained on the surface of the photosensitive drum after the transfer is removed by the cleaning device.
Among charge devices, a contact charge type charge device includes a charge roller as a charge member arranged to contact the photosensitive drum, a power source that applies a voltage to the charge roller, and the like. In the contact charge type charge device, the charge roller contacts the photosensitive drum. Therefore, image quality is decreased if foreign matter, such as the toner, external additive or the like that is not removed by the cleaning device, is attached to the charge roller, preventing the photosensitive drum from being appropriately charged, or if the foreign matter attached to the charge roller is attached to the photosensitive drum, causing the surface of the photosensitive drum to be smudged.
Therefore, a surface treatment using isocyanate and polycarbonate is performed on the surface of the charge roller to harden the surface and to increase release property. As a result, the foreign matter is suppressed from attached to the surface (see JP Laid-Open Patent Application No. 2009-223214, for example).
However, with the conventional charge roller, if the operator's hand touches the surface of the charge roller, for example, while transporting, inspecting or installing the charge roller in the printer, a touch mark is left on the charge roller. As a result, spots appear at the time of forming a halftone image and the like, causing the image quality to be decreased.
One of objects of the present invention is to solve the problems of the conventional charge roller and to provide a charge member, a charge device and an image forming apparatus that prevent the image quality from decreasing.